get all properties of the event object...

 Playing around with mouse/touch/pointer events, I was a annoyed that Object.keys(e) only returns "isTrusted" when there's lots of good information there... 

In short there's all kinds of "own" (meaning not inherited from a parent object) and"enumerable" aspects messing things up, but short answer is that this stackoverflow suggests 

function getAllPropertyNames (obj) {
    const proto     = Object.getPrototypeOf(obj);
    const inherited = (proto) ? getAllPropertyNames(proto) : [];
    return [...new Set(Object.getOwnPropertyNames(obj).concat(inherited))];
}

and has some other more specific functions as well.